Process of reclaiming devulcanized rubber.



UNITED STATES PATENT OFFICE.

ERWIN EMIL ALBERT GEORG MEYER, OF NEW BRUNSWICK, NEW JERSEY.

PROCESS or nncmnlma nnvvncnmzn n RUBBER.

Specification of Letters Patent.

Application filed April 29, 1908. Serial No. 429,808.

Patentedleb. 28, 1909.

following is a specification.

The object of my invention is a process of converting rubber by depolymerization into -a rubber which possesses practically the properties of natural rubber. By the term devulcanized rubber as here used I mean .rubber which has once been vulcanized and afterwardssubjected to a treatment to remove substantially all the added ingredients.

Rubber in the devulcanized state cannot be used for manufacturin pur oses with the same success as natura rub er, but this same devulcanized rubber after it has been subjected to the depolymerizing action of the present invention, assumes again the properties characteristic of natural rubber and can be used in the same manner, and particularly may 'be revulcanized, with practically the same success as natural rubber.

In the manufacture of rubber articles, beside the sulfur necessary for vulcanization mineral matters of various kinds are added andsolidified or oxidized oils and similar substances which are used as rubber substitutes.

In the process of devulcanization all theadded materials-may be separated with comparative ease except the sulfur. According to the modern theory of vulcanization the sulfur enters partly into chemical combination with the rubber while a portion remains as free sulfur, and the vulcanization process I itself is considered to be one of polymerization due to the action of the heat and sulfurcombined.

The ste s and chemicals used in my process differ rom all methods and all processes known in the prior art, in that they apparently depolymerize the hydrocarbons of the rubber substance, without any other change or injurious secondary action, and bring order to carry out my, rocess practically I proceed as follows: Ru ber waste is out n into small ieces and mechanically se arate from text' e fibers and metallic partic es. If the textile fiber is so intimately, mixed with the rubber that it cannot be separated mechanically, the textile fiber must be removed by a carbonizing process with acids. Whatever is done in this preliminary treatment, the rubber waste should not be affected by a concentrated solution, or high pressure or temperature, and should be practically free from moisture before the subse uent addition of the solvents. The dry an comminuted rubber is then treated with a liquid in a strongly built iron vessel provided with a stirring mechanism and condenser, sothat the treatment of the material may be carried on at the boiling point of these liquids. vessel is also connected with a pump which supplies the necessary liquid from two separate tanks.

For each kilo of waste about six liters of liquid is employed. The quantity is, however, entirely dependent on the kind of waste to be treated. The composition of the liquid also de ends upon the grade of waste. In practice I ave found the following proportions to act satisfactorily:

2 parts of rubber solvent ,to 8 parts of acetone 3 (l I (K H, (I 7 I (l (K 4 H H (I H H 6 U H (K As a rubber solvent I can use phenol, chloro- This form, naphtha, gasolene, nitro-benzene, mixtures thereof, or other organic'solvents for rubber. Instead of acetone I can use ethyl alcohol. The treatment usually lasts from two to five hours according to the material, and the temperature to be employed for the treat-.

ment must also be varied accordingly. If such rubber substitutes as factis are present, and it is desired to remove such substances, the following treatment is additionally recommended. An alcoholic solution of caustic soda containing about two. to five per cent. of the alkali is added to therubber waste after the solvents employed in the prior treatment have been removed. Of this solution enough isemploed to perfectlycover the rubber waste: he whole mass is then heated for about two to five hours' -at the boiling point accompames natural rubber, and is tprepared as follows: One hundred kilos 0 rubber resin are heated with two hundred kilos of water, to which twenty kilos of sodium hydroxid are added; the mass is boiled, and to the boiling 1i uid five kilos of sodium carbonate are a ded. For each one hundred kilos of rubber waste treated, ten kilos of resinous soap are taken. Then the rubber is heated with the soap by the admission of steam to a temperature of about 140 to 210 0., and corresponding pressure according to the quality 0 the material to be treated. Durin the last stage of the process I subject the ru ber mass to a high mechanical preslbs. er s uare inch, which is produced the best y a ydraulic ram which acts in the inside of the digester. The treatment maylast from two to five hours.

For some rubber waste it is advantageous to employ a larger quantity of resinous soap, and good results were obtained by increasing the amount of resinous soap to thirty per cent. of the quantity of the waste rubber used in the process. It has also been found that the resins extracted from some qualities of natural rubber do not easily y1eld.soa s which can be successfully employed in t e process of depolymerization. The production of the resinous soap mi ht then advantageously be modified as Follows: To one hundred arts of resin ten parts of cocoanut oil are a ded and this mass is heated with a solution containing ten parts of caustic soda,

dissolved in fifty parts of water, and two parts of sodium carbonate, also dissolved in fifty parts of water. To this mixture two hundred parts of water are gradually added until a complete solution is obtained. The resin soap might also be made by melting together the proper amount of resin with alkali in solid form, and dissolved by boiling with water afterwards.

In employing the resinous soap it is of importance to avoid the presence of free alkali. Careful neutralization of the soap is accom plished by adding the requisite amount of a free fatty acid, like olelc acid, or by such acids as acetic acid, or by phenolic comounds, capable of forming salts with alkales, such as carbolic acid.

"is probable that su sure, of preferably in excess of about 400.-

Although I have above described an example of carrying out my new rocess of depolymerizing devulcanized rub er, I do not wish to be understood as excluding equivalents for the ingredients, the apparatus, or the operations employed in the process. It

stitutes may be employed without departing from the scope of the process intended to be secured thereby.

When I use the term,devulcanized rubber I mean especially rubber waste which has been subjected to a treatment for the removal of sulfur and filling ingredients.

Of course, none of such treatments wholly remove the materials added to the rubber, but the free sulfur should be entirely re moved before the depolymerizin treatment, in order to secure the full desired effect.

What I claim as new is:

1. The process of depolymerizing devulcanized rubber, which consists in] mixing the devulcanizcd rubber with a neutral resinous soap, subjecting the mixture to the action of heat in excess of 120 0., and, during a portion of the treatment, to mechanical pressure.

2. The processof depolymerizing devulcanized rubber, which consists in mixing devulcanized rubber with a neutral resinous soap, subjecting such mixture to the action of heat in excess of 120 C. and finally to the combined action of the heat and a high mechanical pressure.

3. The process of depolymerizing rubber waste, which consists in first devulcanizing the same by treating it with a mixture of two solvents, the one of which is a rubber solvent, while the other is not, then mixing with the devulcanized rubber a neutral resinous soap and subjecting the mixture to a high mechan- 1cal pressure at a temperature in excess of 120 C.

4. The process of depolymerizing rubber waste, which consists in first devulcanizing the same, then mixing with a neutral resinous soa made from the resin of natural rubber an subjecting the mixture to mechanical pressure under the action of heat in excess of 120 C.

'5. The process of depolymerizin rubber waste, which consists in first devuIcanizing the same by treating it with a mixture of two solvents, the one of which is a rubber solvent, while the other is not, adding an alcoholic solution of a hydroxid possessin a saponifying action, and finally treating t e mixture with a neutral soap made from the resin of natural rubber.

6. The process of depolymerizin rubber waste, which consists in first devu canizing the same by treating it with a mixture of two solvents, the one of which is a rubber solvent,

while the other is not, subjecting the devulcanized rubber to the action of an alcoholic solution of a hydroxid possessin a saponi- In witness whereof, I have signed my name lying action, and finally treating t 0 mixture in the presence of two witnesses. at high tem rature with a neutral resinous soa made mm the resin of natural rubber ALBERT GEORG MEYER '5 an associated with an oil capable of saponifi- Witnesses:

cation and at the same time effecting upon H. RICHARD WoBsE,

the solid mixture a high mechanical pressure. M. M. QUEENAN. 

